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DOI: 10.1055/s-2008-1042712
Nanotweezers for Chiral Discrimination of Carbon Nanotubes
Contributor(s):Timothy M. Swager, Kristin L. GlabShiga University of Medical Science, Otsu, Japan
Improved Optical Enrichment of SWNTs through Extraction with Chiral Nanotweezers of 2,6-Pyridylene-Bridged Diporphyrins
J. Am. Chem. Soc. 2007, 129: 15947-15953
Publication History
Publication Date:
21 February 2008 (online)
Key words
porphyrins - carbon nanotubes - optical enrichment
Significance
A single-walled carbon nanotube (SWCNT) may have a left- or right-handed helical structure (designated M and P by IUPAC nomenclature), in accord with the graphene sheet from which the nanotube was formed. To extend the potential applications and fundamental studies of carbon nanotubes, a method for separating the P and M forms is desired. Chiral bisporphyrins 1 and 2 selectively complex with either (P)- or (M)-SWCNTs and thereby enable preferential extraction of one chiral form.
Comment
Optical enrichment of SWCNTs through separation of the P and M forms was first demonstrated by Peng et al. (Nat. Nanotechnol. 2007, 2, 361) by using 1,3-phenylene-bridged diporphyrin 2 to selectively complex either (P)- or (M)-SWCNTs. In this article, Peng et al. achieved higher levels of optical enrichment by complexing SWCNTs with 2,6-pyridylene-bridged diporphyrin 1, as indicated by CD spectra. Additionally, UV-Vis-NIR spectra and extraction yields indicate that SWCNTs are more readily extracted by 1. Computer calculations rationalize these results by indicating that 1, which has a smaller dihedral angle (93.8°) between the porphyrin rings than 2 (111.2°), forms a more stable complex with SWCNTs.